Question

3.The radii of two circles are 19 cm and 9 cm respectively. The radius of the circle which has circumference equal to the sum of the circumference of two circles is-
35 cm
10 cm
21 cm
28 cm
Class 10 Maths​

Answer 1

Let r

1

and C

1

be the radius and circumference, respectively of 1st circle and r

2

and C

2

be the radius and circumference, respectively of 2nd circle.

Let r

3

and C

3

be the radius and circumference, respectively of the required circle.

r

1

=19cm ...Given

Now C

1

=2πr

1

∴C

1

=2π×19=38π cm ...(1)

r

2

=9cm ...Given

Now C

2

=2πr

2

∴C

2

=2π×9=18πcm ...(2)

C

3

=C

1

+C

2

....Given

∴C

3

=38π+18π ....From (1) and (2)

C

3

=56π cm.

2πr

3

=56π

∴r

3

=28 cm

mark as brainliest

Answer 2

Answer:

28 cm

Step-by-step explanation:

28 cm is the correct answer

Let radius of 1 circle = R =19cm

then radius of other circle = r = 9 cm

Also let radius of new circle = x

sum of circumference of these 2 circles= circumference of new circle formed

2πr+2πR=2πx

2π(R+r)= 2πx

R+r=x

19+9=x

x = 28cm

Radius of new circle is 28 cm